1. Field of the Invention
The present invention relates to a process for producing a cyclododecanone compound. More particularly, the present invention relates to a process for producing a cyclododecanone compound by catalytically isomerizing a corresponding epoxycyclododecane compound.
A cyclododecanone compound is useful as a material for producing laurolactam, dodecanedioic acid and dodecane diol.
2. Description of the Related Art
Methods for producing a cyclododecanone by isomerizing a corresponding epoxycyclododecane compound in the presence of a catalyst consisting of a lithium halide are known from a plurality of reports.
For example, German Patent No. 3,744,094 discloses an isomerization of an epoxycyclododecane in the presence of a catalyst consisting of lithium chloride in a reaction medium consisting of N-methylpyrrolidone or N,Nxe2x80x2-dimethylethyleneurea to produce cyclododecanone with a yield of 94%.
Also, German Patent No. 3,601,380 discloses that, by isomerization of 1,2-epoxy-5,9-cyclododecadiene in the presence of a catalyst consisting of sodium iodide in a reaction medium consisting of a polyethylene glycol (NaI: 3 wt %, 195xc2x0 C., 9 hours), cyclododeca-1,7-diene-1-one is produced with a yield of 98.7%.
In each of the above-mentioned methods, however, since a polar solvent is employed as a reaction medium, means for recovering the solvent or for decomposing the solvent must be added to the production system for the target compound and this causes the production cost of the target compound to increase.
Further, the reaction rate of the isomerization reaction is decreased by a dilution effect or a salvation effect of the solvent, and thus the reaction time necessary to effect the isomerization reaction at a conversion close to 100% becomes long. Also, since the reaction is carried out in a batch type reaction system, the above-mentioned methods are unsuitable for industrially producing the target compound in a large quantity with a high efficiency.
Further, SU Patent 407,874 discloses an isomerization reaction of an epoxycyclododecane, in the presence of a catalyst consisting of anhydrous LiBr, in no solvent. In examples of the SU patent, it is reported that when the reaction was carried out in an amount of LiBr of 4% by weight at a reaction temperature of 120 to 130xc2x0 C. for a reaction time of 18 hours or in an amount of LiBr of 3.3% by weight at a reaction temperature of 200xc2x0 C. for a reaction time of 3 hours, the target cyclododecanone was obtained at a yield of 100% or 83.3%.
In the former example, the reaction time is too long, and thus the reaction is not practical, and in the later example, the selection to the target compound is low and a by-product having a high boiling temperature was produced.
The high boiling temperature by-product is disadvantageous in that when the catalyst is recovered from the reaction mixture after the reaction is completed and recycled to the reaction procedure, the high boiling temperature by-product is accumulated in the reaction system to affect the reaction, and thus an additional procedure for removing the high boiling temperature by-product from the reaction mixture becomes necessary.
In this connection, it may be considered that for the purpose of increasing the reaction rate, the concentration of the catalyst in the reaction system should be increased. However, in the method of the former example, since the solubility of LiBr in the reaction system is saturated, the concentration of the catalyst cannot be increased. In the method of the later example, the reaction temperature is established at a high level to increase the reaction rate. This high temperature causes a side reaction to occur, the yield of the target compound to be decreased, and the high boiling temperature by-product to be produced.
Further, Zh. Org. Khim (1990), 26(7), 1497-1500, discloses that when an isomerization reaction of an epoxycyclododecane was carried out in the presence of 2.3 molar % of a catalyst consisting of LiBr (lithium bromide) at a reaction temperature of 150xc2x0 C. for a reaction time of 10 hours, the target cyclododecanone was obtained at a yield of 96.6%, and when the reaction of the epoxycyclododecane was effected in the presence of 1.5 molar % of LiI (lithium iodide) at 150xc2x0 C. for 5 hours, the target cyclododecanone was obtained at a yield of 91.2%. In the case of this report, however, it is assumed that to make the conversion of the epoxycyclododecane close to 100%, a very long reaction time is necessary. Also, the reaction of the report was effected in a batch-type reaction system, and thus no continuous method for the reaction is disclosed in the report.
In the case where a cyclododecanone compound is produced by isomerizing an epoxycyclododecane compound, since the boiling temperature of the epoxycyclododecane compound is approximately equal to that of the cyclododecanone compound, there are many cases in which the separation of the two compounds from each other by distillation is very difficult from an industrial point of view. Also, since the two compounds are similar in physical and chemical properties to each other, the separation on refining of the two compounds by crystallization or extraction is difficult. Therefore, to produce the cyclododecanone compound with a high degree of purity, it is necessary that the conversion of the epoxycyclododecane compound is controlled to approximately 100%. For this purpose, it is possible to increase the reaction temperature or the content of the catalyst.
However, as mentioned above, an increase in the reaction temperature causes frequent occurrence of side reactions and thus the production of the high boiling temperature compounds is promoted and the yield of the target cyclododecanone compound is reduced.
On other hand, as a measure to enhance the conversion of the epoxycyclododecane compound, it is possible to increase the content of the catalyst in the reaction system. However, the increase in the catalyst content may cause a difficulty in the dissolution of the catalyst in the reaction system and may make the cost of the reaction increase. Thus, this measure is not practical.
All of the reaction procedures of the above-mentioned prior arts are carried out in batch type reactor systems and thus are disadvantageous in that the process operations are complicated, the safety of the operations is unsatisfactory and the operation cost is high. In fact, the isomerization reaction is an exothermic reaction. Therefore, when the cyclododecanone compound is industrially produced in a large quantity by the batch type reactor system, a large amount of heat is generated. In practice, it is important to remove the heat with a high efficiency. For example, when a large amount of an epoxycyclododecane compound is catalytically isomerized at a temperature of 200xc2x0 C. in a batch type reactor, since the removal of the generated reaction heat is difficult, the reaction temperature may be rapidly increased to such an extent that a bumping of the liquid reaction mixture occurs.
As mentioned above, in the conventional technology, it has not yet been possible to isomerize the epoxycyclododecane compound in a short reaction time at a conversion of the compound of approximately 100% with a selectivity to the target compound of approximately 100%. Further, since the known isomerization method is carried out in a batch type reactor, the target cyclododecanone compound cannot be continuously and safely provided. Namely, a continuous process for producing the cyclododecanone compound in an industrial scale has not yet been established.
An object of the present invention is to provide a process for continuously producing a cyclododecanone compound in an industrial scale by an isomerization reaction of an epoxycyclododecane compound in the presence of a catalyst comprising lithium bromide and/or lithium iodide, in a relatively short reaction time, with a high conversion of the epoxycyclododecane compound with a high selectivity of the target cyclododecanone compound with high safety.
The above-mentioned object can be attained by the process of the present invention for continuously producing a cyclododecanone compound.
The process of the present invention comprises;
feeding a liquid reaction mixture comprising an epoxycyclododecane compound and a catalyst comprising at least one member selected from lithium bromide and lithium iodide into a frontmost reaction region of a plurality of reaction regions connected to each other in series;
successively passing the liquid reaction mixture through the series of reaction regions to catalytically isomerize the epoxycyclododecane compound to produce a corresponding cyclododecanone compound; and
collecting the resultant reaction mixture containing the cyclododecanone compound from a rearmost reaction region of the series of reaction regions.
In the process of the present invention for continuously producing a cyclododecanone compound, the epoxycyclododecane compound is preferably selected from saturated and unsaturated cycloaliphatic compounds having 12 carbon atoms and provided with an epoxy group.
In the process of the present invention for continuously producing a cyclododecanone compound, the epoxycyclododecane compound is preferably selected from monoepoxycyclododecane, monoepoxycyclododecenes, monoepoxycyclododecadienes or monoepoxycyclododecatrienes.
In the process of the present invention for continuously producing a cyclododecanone compound, the temperature of a portion of the liquid reaction mixture located in a rear part of the series of reaction regions is preferably controlled to be equal to or higher than that in a front part of the series of reaction regions.
In the process of the present invention for continuously producing a cyclododecanone compound, the series of reaction regions are preferably constituted from a plurality of reaction vessels independent from each other and connected to each other in series in a manner such that with respect to a pair of front and back reaction vessels arranged adjacent to each other, the front vessel is connected to the back vessel through a conduit.
In the process of the present invention for continuously producing a cyclododecanone compound, a bottom portion of the front vessel is connected to a top portion of the back vessel through the conduit.
In the process of the present invention for continuously producing a cyclododecanone compound, the series of reaction regions are preferably constituted from a plurality of reaction chambers separated from each other and connected to each other in such a manner that, with respect to a pair of front and back reaction chambers arranged adjacent to each other, a top portion of the front vessel is connected to a top portion of the back vessel through a liquid path through which a portion of the liquid reaction mixture contained in the front vessel is allowed to overflow into the back vessel.
In the process of the present invention, for continuously producing a cyclododecanone compound, the series of reaction regions preferably comprise a plurality of reaction chambers separated from each other with partitions arranged between the reaction chambers and connected to each other in series through at least one hole formed in each of the partitions.
In the process of the present invention for continuously producing a cyclododecanone compound, at least one of the reaction regions is preferably sealed with an inert gas.
In the process of the present invention for continuously producing a cyclododecanone compound, the catalyst is preferably present in an amount of 0.01 to 20 molar % based on the molar amount of the epoxycyclododecane compound.
In the process of the present invention for continuously producing a cyclododecanone compound, the liquid reaction mixture in the series of reaction regions is heated at a temperature of 100 to 350xc2x0 C.
In the process of the present invention for continuously producing a cyclododecanone compound, the temperature of a portion of the liquid reaction mixture located at the outlet portion of the rearmost reaction region is preferably controlled to 0 to 100xc2x0 C. above that at the inlet portion of the frontmost reaction region.
In the process of the present invention for continuously producing a cyclododecanone compound, the liquid reaction mixture preferably passes through the series of reaction regions in a time of 0.1 to 24 hours.